The present invention relates to a cover layer on at least one electrical conductor and/or semiconductor, especially of an electric sensor.
Cover layers for electrical conductors are known (DE-23 04 464 C2). They consist for example of barium-aluminum silicates, applied using the usual methods employed in ceramics technology. Such coatings are generally gas-tight cover layers.
In addition, porous cover layers are also known that consist for example of a metal, a metal alloy, an oxide, or a mixed oxide such as magnesium spinel, carbides, borides, nitrites of transition metals, or silicate minerals such as high-melting sintered glass or fireproof ceramic materials for example, which can also be applied as raw materials or mixtures of raw materials such as kaolin or talc, possibly with the addition of fluxes such as feldspar, nepheline syenite, or wollastonite, and then sintered.
In known protective layers, the gas-tight cover layer is applied to a solid electrolyte, while the porous first protective layer is located above the electrodes.
It has been found that when electrical conductors are covered with gas-tight cover layers, ions such as calcium, sodium, or oxygen ions migrate under the influence of the electrical voltages applied to the conductors, especially at higher temperatures, causing damage in the first protective layer and consequently in the conductors as well. In addition, discharges of oxygen ions can also release oxygen bubbles.